Docs/platforms/esp32c3: Add BLE sleep

Add BLE sleep docs for esp32[-c3]

Signed-off-by: Eren Terzioglu <eren.terzioglu@espressif.com>

Documentation/platforms/risc-v/esp32c3/boards/esp32c3-devkit/index.rst

@@ -154,6 +154,9 @@ Get the list of BLE devices found around you::
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     nsh>
 
+To decrease power consumption, ``CONFIG_ESPRESSIF_AUTO_SLEEP`` needs to be enabled. This option
+makes the device automatically enter the low power consumption mode when in the idle state
+
 bmp180
 ------